The present invention relates to decals comprising a colored motif, as well as to a method of obtaining a vulcanized rubber tire having a colored motif on one of its outer surfaces.
The interest displayed by customers in the aesthetic appearance of the articles which they may purchase is increasing. In fact, it is well known that an article which has a visible decoration and, what is more, decorations in different colors, represents an additional attraction. Furthermore, as is the case in the tire industry, the standards in force require an increasing number of markings on the sidewalls of tires; it therefore appears particularly useful to be able to distinguish some of these markings from others, and one of the means of accomplishing this is by depositing on the outer surface of a tire at least one colored ink employed in accordance with a motif corresponding to the marking desired.
It is known, for instance from U.S. Pat. No. 2,188,866, to apply a decal comprising a colored motif in order to decorate the outer surface of an article of vulcanized rubber, such as, for instance, a vulcanized tire. U.S. Pat. No. 2,188,866 discloses a decal comprising a temporary support on which at least one colored ink has been deposited, in accordance with a predetermined motif, in a relatively slight thickness as compared with the thickness of the support. This ink is so formulated that it can be transferred onto the article to be decorated under conditions of pressure and temperature which are suitable in order to obtain good adherence on a previously vulcanized rubber mix while remaining sufficiently elastic after transfer. By elastic, it is understood that the ink transferred is sufficiently deformable to be able to follow the deformations of the surface of the article onto which it has been transferred during the subsequent use of said article.
One of the difficulties encountered in the development and carrying out of such a method for decorating articles, such as tires, resides in the fact that it is difficult to position the decal accurately on the tire before effecting the transfer of the motif. This difficulty is related to the geometry of the surface on which this decal is placed and the texture of said surface (grooves, hollows, bosses, more or less slippery conditions, etc.). It is easily seen that it is necessary to position the decal properly so that, after the transfer of the ink from the motif onto the tire, the motif is in a position which has been previously selected; this correct positioning requires a relatively lengthy period of adjustment which, from an industrial standpoint, limits the use of a decal in order to produce a decoration on a vulcanized tire.
Furthermore, it may happen that the motif, even though correctly positioned on the tire to be decorated, is not properly oriented with respect to the tire itself; this may take place in the event that it is desired to indicate by means of an arrow a preferred direction of a tire provided with a tread which establishes a preferred direction of rotation for the tire. This leads to the necessity of additional operations of verification after the putting in place of a motif by thermal transfer; these verifications are, to be sure, expensive and are not without an influence on the final price of the product provided with a motif.
It must be added that defects in the position and/or orientation of a motif are particularly visible since said motif is in general of a different color than that of the tire. The presence of these defects makes it necessary in most cases to act, after the transfer of the motif, in order to eliminate said motif, which cannot be done easily, the ink having been formulated to adhere well to the rubber, and it requires a special tool; despite everything, the operation, however, remains difficult and may leave traces on the tire.
In order to reduce the defects in the positioning of a decal, it is possible to use complicated systems which employ luminous markers, the worker having to place the decal manually in the proper place with the proper orientation guided by luminous markings created on the surface of the tire; an alternative is to provide a device which has the function of depositing the decal in the proper place. The drawbacks inherent in these systems are of a financial nature since it is necessary to invest in costly machines (and in sufficient number).